1. Technical Field
The present application relates generally to nanotube fabrics and methods of making same and, more specifically to carbon nanotube fabrics and methods of making same for use in light emitting systems.
2. Discussion of Related Art
Opto-electronics technologies have been utilized and developed in various fields such as the information input/output technologies and the optical communication technologies using optical fibers, and so on. Laser diodes have been developed as devices which support these opto-electronics technologies. For example, laser diodes can be used for reading compact discs and they can be used in optical communications.
Light emitting diodes (LEDs) are special p-n junctions that are designed for optimum electroluminescence as described in Kwok K. NG, “Complete Guide to Semiconductor Devices,” IEEE Press, John Wiley & Sons, 2002, pages 396-404. Semiconductor materials, mostly III-V compounds are used, although some II-VI compounds are used as well. Doped active films are usually grown epitaxially on substrates such as GaAs, GaP, and InP. LEDs emit in a well-defined portion of the spectrum at particular wavelengths and with corresponding colors as illustrated in FIG. 51.2 of the above NG reference. These devices are usually discrete, do not integrate with silicon, and usually emit a particular color, with multiple LEDs required to obtain a near-white light (in those applications where near-white light is desirable).
Photodiodes are p-n diodes or p-i-n diodes that absorb light as described in Kwok K. NG, “Complete Guide to Semiconductor Devices,” IEEE Press, John Wiley & Sons, 2002, pages 431-435. Photodiodes typically operate under a moderate reverse bias with reverse bias current increasing rapidly with absorbed light (radiation). Photodiodes are often fabricated in silicon substrates and integrate well with various devices and circuits. Photodiode speed of operation has been demonstrated in excess of 30 GHz.
Currently, light emitters used for optoelectronic applications in the semiconductor industry are typically micron-sized and cannot be monolithically integrated but are discrete components. There is therefore a need in the art for large scale fabrication methods of nanoscale light emitters used for electronic applications in the semiconductor industry which can be monolithically integrated into a CMOS or similar process flow to fabricate integrated circuits. Naturally, the uses of such elements extend to most types of consumer electronics where light emission in integrated elements is beneficial.
Misewich et al. have reported IR light emission from single-walled nanotubes (SWNT) (See “Electrically Induced Optical Emission from a Carbon Nanotube FET,” Science 200 (2003) 783-786). IBM's research team detected light with a wavelength of 1.5 micrometers, which is particularly valuable because it is the wavelength widely used in optical communications. Nanotubes with different diameters could generate light with different wavelengths used in other applications. The investigators report that the mechanism for light emission in the structures studied is electron-hole recombination.
Wei et al. report the use of carbon nanotubes as incandescent light sources which operate by black body radiation and at higher temperatures, perhaps by some other mechanism such as electron/hole recombination. (See “Carbon Nanotube Filaments in Household Lightbulbs,” Appl. Phys. Lett. 84 (2004) 4869-4871.)